Oh, I know it. I've been driving myself crazy with the safety of the seating in our bus.

Buses in the US usually don't have seatbelts, either - likewise because the higher seat backs catch the flying kids (and because school bus drivers are so highly trained). But the other reason that doesn't get reported often is this: when you attach kids to the bus seats with seatbelts, it increases the load on the seats in the event of a crash - so much so that there have been incidents where the bolts that hold the seats to the floor have ripped through the sheet metal, causing the seats (with children attached) to catapult forward in a twisting way since they usually stay attached to the sidewall.
We considered welding LATCHes onto our seats, but have decided against it, since I doubt we could get the welds strong enough (researching the LATCH system, I've found out that the lower anchors are supposed to withstand 1.8 tons of force each in a crash, while the tether anchor is supposed to withstand 2.4 tons of force - so that's 6 tons of force PER KID, or 12 tons PER SEAT). But then I also learned that a lot of vehicles' LATCHes fail in crashes anyway, and I also reason that a 15 ton bus is going to decelerate more slowly than a minivan in a crash - unless, of course, you crash head-on into another bus or a mountain or something of significant mass).
Anyway, in the end, we decided to go with the complete overkill method, and reinforce the steel floor to prevent the bolts from ripping through, and we'll attach the car seats to the bus seat bars with reinforced straps that are used in industrial settings to lift many tons of weight. I am probably overthinking this, but the automotive industry has many decades of experience in safety features, and I'm sure they know something I haven't thought of.